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Waiman Long
9a5418bc48
Commit851a723e45("sched: Always clear user_cpus_ptr in do_set_cpus_allowed()") may call kfree() if user_cpus_ptr was previously set. Unfortunately, some of the callers of do_set_cpus_allowed() may have pi_lock held when calling it. So the following splats may be printed especially when running with a PREEMPT_RT kernel: WARNING: possible circular locking dependency detected BUG: sleeping function called from invalid context To avoid these problems, kfree_rcu() is used instead. An internal cpumask_rcuhead union is created for the sole purpose of facilitating the use of kfree_rcu() to free the cpumask. Since user_cpus_ptr is not being used in non-SMP configs, the newly introduced alloc_user_cpus_ptr() helper will return NULL in this case and sched_setaffinity() is modified to handle this special case. Fixes:851a723e45("sched: Always clear user_cpus_ptr in do_set_cpus_allowed()") Suggested-by: Peter Zijlstra <[email protected]> Signed-off-by: Waiman Long <[email protected]> Signed-off-by: Ingo Molnar <[email protected]> Reviewed-by: Peter Zijlstra <[email protected]> Link: https://lore.kernel.org/r/[email protected]